diff --git a/core/src/mindustry/world/blocks/ConstructBlock.java b/core/src/mindustry/world/blocks/ConstructBlock.java
index df7434a222..15553854a9 100644
--- a/core/src/mindustry/world/blocks/ConstructBlock.java
+++ b/core/src/mindustry/world/blocks/ConstructBlock.java
@@ -166,6 +166,7 @@ public class ConstructBlock extends Block{
 
         private float[] accumulator;
         private float[] totalAccumulator;
+        private int[] itemsLeft;
 
         @Override
         public String getDisplayName(){
@@ -270,7 +271,7 @@ public class ConstructBlock extends Block{
 
             for(int i = 0; i < current.requirements.length; i++){
                 int reqamount = Math.round(state.rules.buildCostMultiplier * current.requirements[i].amount);
-                accumulator[i] += Math.min(reqamount * maxProgress, reqamount - totalAccumulator[i] + 0.00001f); //add min amount progressed to the accumulator
+                accumulator[i] += Math.min(reqamount * maxProgress, reqamount - totalAccumulator[i]); //add min amount progressed to the accumulator
                 totalAccumulator[i] = Math.min(totalAccumulator[i] + reqamount * maxProgress, reqamount);
             }
 
@@ -279,9 +280,28 @@ public class ConstructBlock extends Block{
             progress = Mathf.clamp(progress + maxProgress);
 
             if(progress >= 1f || state.rules.infiniteResources){
-                if(lastBuilder == null) lastBuilder = builder;
-                if(!net.client()){
-                    constructed(tile, current, lastBuilder, (byte)rotation, builder.team, config);
+                boolean canFinish = true;
+
+                //look at leftover resources to consume, get them from the core if necessary, delay building if not
+                if(!state.rules.infiniteResources){
+                    for(int i = 0; i < itemsLeft.length; i++){
+                        if(itemsLeft[i] > 0){
+                            if(core != null && core.items.has(current.requirements[i].item, itemsLeft[i])){
+                                core.items.remove(current.requirements[i].item, itemsLeft[i]);
+                                itemsLeft[i] = 0;
+                            }else{
+                                canFinish = false;
+                                break;
+                            }
+                        }
+                    }
+                }
+
+                if(canFinish){
+                    if(lastBuilder == null) lastBuilder = builder;
+                    if(!net.client()){
+                        constructed(tile, current, lastBuilder, (byte)rotation, builder.team, config);
+                    }
                 }
             }
         }
@@ -321,6 +341,7 @@ public class ConstructBlock extends Block{
                         int accepting = Math.min(accumulated, core.storageCapacity - core.items.get(requirements[i].item));
                         //transfer items directly, as this is not production.
                         core.items.add(requirements[i].item, accepting);
+                        itemsLeft[i] -= accepting;
                         accumulator[i] -= accepting;
                     }else{
                         accumulator[i] -= accumulated;
@@ -331,6 +352,14 @@ public class ConstructBlock extends Block{
             progress = Mathf.clamp(progress - amount);
 
             if(progress <= current.deconstructThreshold || state.rules.infiniteResources){
+                //add any leftover items that weren't obtained due to rounding errors
+                if(core != null){
+                    for(int i = 0; i < itemsLeft.length; i++){
+                        core.items.add(current.requirements[i].item, Mathf.clamp(itemsLeft[i], 0, core.storageCapacity - core.items.get(current.requirements[i].item)));
+                        itemsLeft[i] = 0;
+                    }
+                }
+
                 if(lastBuilder == null) lastBuilder = builder;
                 Call.deconstructFinish(tile, this.current, lastBuilder);
             }
@@ -341,6 +370,11 @@ public class ConstructBlock extends Block{
             boolean infinite = team.rules().infiniteResources || state.rules.infiniteResources;
 
             for(int i = 0; i < current.requirements.length; i++){
+                //there is no need to remove items that have already been fully taken out
+                if(itemsLeft[i] == 0){
+                    continue;
+                }
+
                 int sclamount = Math.round(state.rules.buildCostMultiplier * current.requirements[i].amount);
                 int required = (int)(accumulator[i]); //calculate items that are required now
 
@@ -360,6 +394,7 @@ public class ConstructBlock extends Block{
                     //remove stuff that is actually used
                     if(remove && !infinite){
                         inventory.remove(current.requirements[i].item, maxUse);
+                        itemsLeft[i] -= maxUse;
                     }
                 }
                 //else, no items are required yet, so just keep going
@@ -368,6 +403,7 @@ public class ConstructBlock extends Block{
             return maxProgress;
         }
 
+        @Override
         public float progress(){
             return progress;
         }
@@ -380,8 +416,14 @@ public class ConstructBlock extends Block{
             this.current = block;
             this.previous = previous;
             this.buildCost = block.buildCost * state.rules.buildCostMultiplier;
+            this.itemsLeft = new int[block.requirements.length];
             this.accumulator = new float[block.requirements.length];
             this.totalAccumulator = new float[block.requirements.length];
+
+            ItemStack[] requirements = current.requirements;
+            for(int i = 0; i < requirements.length; i++){
+                this.itemsLeft[i] = Mathf.round(requirements[i].amount * state.rules.buildCostMultiplier);
+            }
             pathfinder.updateTile(tile);
         }
 
@@ -394,8 +436,14 @@ public class ConstructBlock extends Block{
             this.progress = 1f;
             this.current = previous;
             this.buildCost = previous.buildCost * state.rules.buildCostMultiplier;
+            this.itemsLeft = new int[previous.requirements.length];
             this.accumulator = new float[previous.requirements.length];
             this.totalAccumulator = new float[previous.requirements.length];
+
+            ItemStack[] requirements = current.requirements;
+            for(int i = 0; i < requirements.length; i++){
+                this.itemsLeft[i] = Mathf.round(requirements[i].amount * state.rules.buildCostMultiplier * state.rules.deconstructRefundMultiplier);
+            }
             pathfinder.updateTile(tile);
         }